NAME

SYNOPSIS

DESCRIPTION

ksh
is a command interpreter intended for both interactive and shell
script use.
Its command language is a superset of the
sh(1)
shell language.

The options are as follows:

-c string

ksh
will execute the command(s) contained in
string.

-i

Interactive shell.
A shell is
interactive
if this
option is used or if both standard input and standard error are attached
to a
tty(4).
An interactive shell has job control enabled, ignores the
SIGINT,
SIGQUIT,
and
SIGTERM
signals, and prints prompts before reading input (see the
PS1
and
PS2
parameters).
For non-interactive shells, the
trackall
option is on by default (see the
set
command below).

-l

Login shell.
If the basename the shell is called with (i.e. argv[0])
starts with
"-"
or if this option is used,
the shell is assumed to be a login shell and the shell reads and executes
the contents of
/etc/profile
and
$HOME/.profile
if they exist and are readable.

-p

Privileged shell.
A shell is
privileged
if this option is used
or if the real user ID or group ID does not match the
effective user ID or group ID (see
getuid(2)
and
getgid(2/)).
A privileged shell does not process
$HOME/.profile
nor the
ENV
parameter (see below).
Instead, the file
/etc/suid_profile
is processed.
Clearing the privileged option causes the shell to set
its effective user ID (group ID) to its real user ID (group ID).

-r

Restricted shell.
A shell is
restricted
if this
option is used;
if the basename the shell was invoked with was
rksh;
or if the
SHELL
parameter is set to
rksh.
The following restrictions come into effect after the shell processes any
profile and
ENV
files:

The shell reads commands from standard input; all non-option arguments
are positional parameters.

In addition to the above, the options described in the
set
built-in command can also be used on the command line:
both
[-+abCefhkmnuvXx]
and
[-+o option]
can be used for single letter or long options, respectively.

If neither the
-c
nor the
-s
option is specified, the first non-option argument specifies the name
of a file the shell reads commands from.
If there are no non-option
arguments, the shell reads commands from the standard input.
The name of the shell (i.e. the contents of $0)
is determined as follows: if the
-c
option is used and there is a non-option argument, it is used as the name;
if commands are being read from a file, the file is used as the name;
otherwise, the basename the shell was called with (i.e. argv[0]) is used.

If the
ENV
parameter is set when an interactive shell starts (or,
in the case of login shells,
after any profiles are processed), its value is subjected to parameter,
command, arithmetic, and tilde
(~)
substitution and the resulting file
(if any) is read and executed.
In order to have an interactive (as opposed to login) shell
process a startup file,
ENV
may be set and exported (see below) in
$HOME/.profile
\- future interactive shell invocations will process any file pointed to by
$ENV:

export ENV=$HOME/.kshrc

$HOME/.kshrc
is then free to specify instructions for interactive shells.
For example, the global configuration file may be sourced:

\&. /etc/ksh.kshrc

The above strategy may be employed to keep
setup procedures for login shells in
$HOME/.profile
and setup procedures for interactive shells in
$HOME/.kshrc.
Of course, since login shells are also interactive,
any commands placed in
$HOME/.kshrc
will be executed by login shells too.

The exit status of the shell is 127 if the command file specified on the
command line could not be opened, or non-zero if a fatal syntax error
occurred during the execution of a script.
In the absence of fatal errors,
the exit status is that of the last command executed, or zero, if no
command is executed.

Command syntax

The shell begins parsing its input by breaking it into
words.
Words, which are sequences of characters, are delimited by unquoted whitespace
characters (space, tab, and newline) or meta-characters
(
"\*(Lt",
"\*(Gt",
"\*(Ba",
"\&;",
"(",
"\&)",
and
"&"
).
Aside from delimiting words, spaces and tabs are ignored, while newlines
usually delimit commands.
The meta-characters are used in building the following
tokens:
"\*(Lt",
"\*(Lt&",
"\*(Lt\*(Lt",
"\*(Gt",
"\*(Gt&",
"\*(Gt\*(Gt",
etc. are used to specify redirections (see
below);
"\*(Ba"
is used to create pipelines;
"\*(Ba&"
is used to create co-processes (see
below);
"\&;"
is used to separate commands;
"&"
is used to create asynchronous pipelines;
"&&"
and
"||"
are used to specify conditional execution;
"";;
is used in
case
statements;
"(("....))
is used in arithmetic expressions;
and lastly,
"\&(".. )\&
is used to create subshells.

Whitespace and meta-characters can be quoted individually using a backslash
(\e),
or in groups using double
(\&")
or single
(')
quotes.
Note that the following characters are also treated specially by the
shell and must be quoted if they are to represent themselves:
"\e",
"\&"",
"'",
"#",
"$",
"`",
"~",
"{",
"}",
"*",
"\&?",
and
"[".
The first three of these are the above mentioned quoting characters (see
below);
"#",
if used at the beginning of a word, introduces a comment \(em everything after
the
"#"
up to the nearest newline is ignored;
"$"
is used to introduce parameter, command, and arithmetic substitutions (see
below);
"`"
introduces an old-style command substitution (see
below);
"~"
begins a directory expansion (see
below);
"{"
and
"}"
delimit
csh(1/Ns)
alterations (see
below);
and finally,
"*",
"\&?",
and
""[
are used in file name generation (see
below).

As words and tokens are parsed, the shell builds commands, of which there
are two basic types:
simple-commands,
typically programs that are executed, and
compound-commands,
such as
for
and
if
statements, grouping constructs, and function definitions.

A simple-command consists of some combination of parameter assignments
(see
below),
input/output redirections (see
below),
and command words; the only restriction is that parameter assignments come
before any command words.
The command words, if any, define the command
that is to be executed and its arguments.
The command may be a shell built-in command, a function,
or an external command
(i.e. a separate executable file that is located using the
PATH
parameter; see
below).
Note that all command constructs have an exit status: for external commands,
this is related to the status returned by
wait(2)
(if the command could not be found, the exit status is 127; if it could not
be executed, the exit status is 126); the exit status of other command
constructs (built-in commands, functions, compound-commands, pipelines, lists,
etc.) are all well-defined and are described where the construct is
described.
The exit status of a command consisting only of parameter
assignments is that of the last command substitution performed during the
parameter assignment or 0 if there were no command substitutions.

Commands can be chained together using the
"|"
token to form pipelines, in which the standard output of each command but the
last is piped (see
pipe(2))
to the standard input of the following command.
The exit status of a pipeline is that of its last command.
A pipeline may be prefixed by the
"\&!"
reserved word, which causes the exit status of the pipeline to be logically
complemented: if the original status was 0, the complemented status will be 1;
if the original status was not 0, the complemented status will be 0.

Lists
of commands can be created by separating pipelines by any of the following
tokens:
"&&",
"||",
"&",
"|&",
and
"\&;".
The first two are for conditional execution:
cmd1&& cmd2
executes
cmd2
only if the exit status of
cmd1
is zero;
"||"
is the opposite \(em
cmd2
is executed only if the exit status of
cmd1
is non-zero.
"&&"
and
"||"
have equal precedence which is higher than that of
"&",
"|&",
and
"\&;",
which also have equal precedence.
Note that the
"&&"
and
"||"
operators are
"left-associative".
For example, both of these commands will print only
"bar":

$ false && echo foo || echo bar
$ true || echo foo && echo bar

The
"&"
token causes the preceding command to be executed asynchronously; that is,
the shell starts the command but does not wait for it to complete (the shell
does keep track of the status of asynchronous commands; see
below).
When an asynchronous command is started when job control is disabled
(i.e. in most scripts), the command is started with signals
SIGINT
and
SIGQUIT
ignored and with input redirected from
/dev/null
(however, redirections specified in the asynchronous command have precedence).
The
"|&"
operator starts a co-process which is a special kind of asynchronous process
(see
below).
Note that a command must follow the
"&&"
and
"||"
operators, while it need not follow
"&",
"|&",
or
"\&;".
The exit status of a list is that of the last command executed, with the
exception of asynchronous lists, for which the exit status is 0.

Compound commands are created using the following reserved words.
These words
are only recognized if they are unquoted and if they are used as the first
word of a command (i.e. they can't be preceded by parameter assignments or
redirections):

case else function then !
do esac if time [[
done fi in until {
elif for select while }

Note:
Some shells (but not this one) execute control structure commands in a
subshell when one or more of their file descriptors are redirected, so any
environment changes inside them may fail.
To be portable, the
exec
statement should be used instead to redirect file descriptors before the
control structure.

In the following compound command descriptions, command lists (denoted as
list)
that are followed by reserved words must end with a semicolon, a newline, or
a (syntactically correct) reserved word.
For example, the following are all valid:

Execute
list
in a subshell.
There is no implicit way to pass environment changes from a
subshell back to its parent.

{ list; }

Compound construct;
list
is executed, but not in a subshell.
Note that
"{"
and
"}"
are reserved words, not meta-characters.

.Oo Op (
\pattern
[\*(Ba pattern]
... )
list;;\ \& Oc ... esac
The
case
statement attempts to match
word
against a specified
pattern;
the
list
associated with the first successfully matched pattern is executed.
Patterns used in
case
statements are the same as those used for file name patterns except that the
restrictions regarding
"\&."
and
"/"
are dropped.
Note that any unquoted space before and after a pattern is
stripped; any space within a pattern must be quoted.
Both the word and the
patterns are subject to parameter, command, and arithmetic substitution, as
well as tilde substitution.
For historical reasons, open and close braces may be used instead of
in
and
esac
e.g.\&
case$foo { *) echo bar; }.
The exit status of a
case
statement is that of the executed
list;
if no
list
is executed, the exit status is zero.

.Oo in Ar word No ... Oc ;
do list; done
For each
word
in the specified word list, the parameter
name
is set to the word and
list
is executed.
If
in
is not used to specify a word list, the positional parameters
($1, $2, etc.)\&
are used instead.
For historical reasons, open and close braces may be used instead of
do
and
done
e.g.\&
fori; { echo $i; }.
The exit status of a
for
statement is the last exit status of
list;
if
list
is never executed, the exit status is zero.

then list;
.Oo elif Ar list ;
then list; Oc
...
.Oo else Ar list ; Oc
fi
If the exit status of the first
list
is zero, the second
list
is executed; otherwise, the
list
following the
elif,
if any, is executed with similar consequences.
If all the lists following the
if
and
elif
fail (i.e. exit with non-zero status), the
list
following the
else
is executed.
The exit status of an
if
statement is that of non-conditional
list
that is executed; if no non-conditional
list
is executed, the exit status is zero.

.Oo in Ar word No ... Oc ;
do list; done
The
select
statement provides an automatic method of presenting the user with a menu and
selecting from it.
An enumerated list of the specified
word
is printed on standard error, followed by a prompt
(
PS3:normally
#?\ \&
).
A number corresponding to one of the enumerated words is then read from
standard input,
name
is set to the selected word (or unset if the selection is not valid),
REPLY
is set to what was read (leading/trailing space is stripped), and
list
is executed.
If a blank line (i.e. zero or more
IFS
characters) is entered, the menu is reprinted without executing
list.

When
list
completes, the enumerated list is printed if
REPLY
is
NULL,
the prompt is printed, and so on.
This process continues until an end-of-file
is read, an interrupt is received, or a
break
statement is executed inside the loop.
If
in word...
is omitted, the positional parameters are used
(i.e. $1, $2, etc.).
For historical reasons, open and close braces may be used instead of
do
and
done
e.g.\&
selecti; { echo $i; }.
The exit status of a
select
statement is zero if a
break
statement is used to exit the loop, non-zero otherwise.

do list;
done
This works like
while,
except that the body is executed only while the exit status of the first
list
is non-zero.

do list;
done
A
while
is a pre-checked loop.
Its body is executed as often as the exit status of the first
list
is zero.
The exit status of a
while
statement is the last exit status of the
list
in the body of the loop; if the body is not executed, the exit status is zero.

{ list; }
Defines the function
name
(see
below).
Note that redirections specified after a function definition are
performed whenever the function is executed, not when the function definition
is executed.

name

Mostly the same as
function
(see
below).

[pipeline]
The
time
reserved word is described in the
section.

(( expression))

The arithmetic expression
expression
is evaluated; equivalent to
let expression
(see
and the
let
command, below).

[[\\&expression\ \&]]

Similar to the
test
and
\&[... \&]
commands (described later), with the following exceptions:

Field splitting and file name generation are not performed on arguments.

The
-a
(AND)
and
-o
(OR)
operators are replaced with
"&&"
and
"||",
respectively.

Operators (e.g.\&
-f,
=,
\&!)
must be unquoted.

The second operand of the
!=
and
=
expressions are patterns (e.g. the comparison
[[foobar = f*r]]
succeeds).

There are two additional binary operators,
"\*(Lt"
and
"\*(Gt",
which return true if their first string operand is less than, or greater than,
their second string operand, respectively.

The single argument form of
test,
which tests if the argument has a non-zero length, is not valid; explicit
operators must always be used e.g. instead of
\&[ str\&]
use
\&[[ -n str\&]].

Parameter, command, and arithmetic substitutions are performed as expressions
are evaluated and lazy expression evaluation is used for the
"&&"
and
"||"
operators.
This means that in the following statement,
$(\*(Ltfoo)
is evaluated if and only if the file
foo
exists and is readable:

$ [[ -r foo && $(\*(Lt foo) = b*r ]]

Quoting

Quoting is used to prevent the shell from treating characters or words
specially.
There are three methods of quoting.
First,
"\e"
quotes the following character, unless it is at the end of a line, in which
case both the
"\e"
and the newline are stripped.
Second, a single quote
(')
quotes everything up to the next single quote (this may span lines).
Third, a double quote
(\&")
quotes all characters, except
"$",
"`"
and
"\e",
up to the next unquoted double quote.
"$"
and
"`"
inside double quotes have their usual meaning (i.e. parameter, command, or
arithmetic substitution) except no field splitting is carried out on the
results of double-quoted substitutions.
If a
"\e"
inside a double-quoted string is followed by
"\e",
"$",
"`",
or
"\&"",
it is replaced by the second character; if it is followed by a newline, both
the
"\e"
and the newline are stripped; otherwise, both the
"\e"
and the character following are unchanged.

Note:
See
below for a special rule regarding
differences in quoting when the shell is in POSIX mode.

Aliases

There are two types of aliases: normal command aliases and tracked aliases.
Command aliases are normally used as a short hand for a long or often used
command.
The shell expands command aliases (i.e. substitutes the alias name
for its value) when it reads the first word of a command.
An expanded alias is re-processed to check for more aliases.
If a command alias ends in a
space or tab, the following word is also checked for alias expansion.
The alias expansion process stops when a word that is not an alias is found,
when a quoted word is found, or when an alias word that is currently being
expanded is found.

Tracked aliases allow the shell to remember where it found a particular
command.
The first time the shell does a path search for a command that is
marked as a tracked alias, it saves the full path of the command.
The next
time the command is executed, the shell checks the saved path to see that it
is still valid, and if so, avoids repeating the path search.
Tracked aliases can be listed and created using
alias-t.
Note that changing the
PATH
parameter clears the saved paths for all tracked aliases.
If the
trackall
option is set (i.e.\&
set-o trackall
or
set-h),
the shell tracks all commands.
This option is set automatically for non-interactive shells.
For interactive shells, only the following commands are
automatically tracked:
cat(1),
cc(1),
chmod(1),
cp(1),
date(1),
ed(1),
emacs(1),
grep(1),
ls(1),
mail(1),
make(1),
mv(1),
pr(1),
rm(1),
sed(1),
sh(1),
vi(1),
and
who(1).

Substitution

The first step the shell takes in executing a simple-command is to perform
substitutions on the words of the command.
There are three kinds of
substitution: parameter, command, and arithmetic.
Parameter substitutions,
which are described in detail in the next section, take the form
.Pf $ Ns Ar name
or
.Pf ${ Ns Ar ... Ns } ;
command substitutions take the form
.Pf $( Ns Ar command Ns \&)
or
.Pf ` Ns Ar command Ns ` ;
and arithmetic substitutions take the form
.Pf $(( Ns Ar expression Ns )) .

If a substitution appears outside of double quotes, the results of the
substitution are generally subject to word or field splitting according to
the current value of the
IFS
parameter.
The
IFS
parameter specifies a list of characters which are used to break a string up
into several words; any characters from the set space, tab, and newline that
appear in the
IFS
characters are called
IFS whitespace.
Sequences of one or more
IFS
whitespace characters, in combination with zero or one
.Pf non- Ev IFS
whitespace
characters, delimit a field.
As a special case, leading and trailing
IFS
whitespace is stripped (i.e. no leading or trailing empty field is created by
it); leading
.Pf non- Ev IFS
whitespace does create an empty field.

Example: If
IFS
is set to
\*(Ltspace\*(Gt:,
and VAR is set to
\*(Ltspace\*(GtA\*(Ltspace\*(Gt:\*(Ltspace\*(Gt\*(Ltspace\*(GtB::D,
the substitution for $VAR results in four fields:
A,
B,

(an empty field),
and
D.
Note that if the
IFS
parameter is set to the
NULL
string, no field splitting is done; if the parameter is unset, the default
value of space, tab, and newline is used.

Also, note that the field splitting applies only to the immediate result of
the substitution.
Using the previous example, the substitution for $VAR:E
results in the fields:
A,
B,
,
and
D:E,
not
A,
B,
,
D,
and
E.
This behavior is POSIX compliant, but incompatible with some other shell
implementations which do field splitting on the word which contained the
substitution or use
IFS
as a general whitespace delimiter.

The results of substitution are, unless otherwise specified, also subject to
brace expansion and file name expansion (see the relevant sections below).

A command substitution is replaced by the output generated by the specified
command, which is run in a subshell.
For
.Pf $( Ns Ar command Ns \&)
substitutions, normal quoting rules are used when
command
is parsed; however, for the
.Pf ` Ns Ar command Ns `
form, a
"\e"
followed by any of
"$",
"`",
or
"\e"
is stripped (a
"\e"
followed by any other character is unchanged).
As a special case in command substitutions, a command of the form
.Pf \*(Lt Ar file
is interpreted to mean substitute the contents of
file.
Note that
$(\*(Ltfoo)
has the same effect as
$(catfoo),
but it is carried out more efficiently because no process is started.

Note:
.Pf $( Ns Ar command Ns \&)
expressions are currently parsed by finding the matching parenthesis,
regardless of quoting.
This should be fixed soon.

Arithmetic substitutions are replaced by the value of the specified expression.
For example, the command
echo$((2+3*4))
prints 14.
See
for a description of an expression.

Parameters

Parameters are shell variables; they can be assigned values and their values
can be accessed using a parameter substitution.
A parameter name is either one
of the special single punctuation or digit character parameters described
below, or a letter followed by zero or more letters or digits
(
"_"
counts as a letter
).
The latter form can be treated as arrays by appending an array index of the
form
[expr]
where
expr
is an arithmetic expression.
Array indices are currently limited to the range 0 through 2047, inclusive.
Parameter substitutions take the form
.Pf $ Ns Ar name ,
.Pf ${ Ns Ar name Ns } ,
or
.Sm off
.Pf ${ Ar name Oo Ar expr Oc }
.Sm on
where
name
is a parameter name.
If substitution is performed on a parameter
(or an array parameter element)
that is not set, a null string is substituted unless the
nounset
option
(
set-o nounset
or
set-u
)
is set, in which case an error occurs.

Parameters can be assigned values in a number of ways.
First, the shell implicitly sets some parameters like
"#",
"PWD",
and
"$";
this is the only way the special single character parameters are set.
Second, parameters are imported from the shell's environment at startup.
Third, parameters can be assigned values on the command line: for example,
FOO=bar
sets the parameter
FOO
to
bar;
multiple parameter assignments can be given on a single command line and they
can be followed by a simple-command, in which case the assignments are in
effect only for the duration of the command (such assignments are also
exported; see below for the implications of this).
Note that both the parameter name and the
"="
must be unquoted for the shell to recognize a parameter assignment.
The fourth way of setting a parameter is with the
export,
readonly,
and
typeset
commands; see their descriptions in the
section.
Fifth,
for
and
select
loops set parameters as well as the
getopts,
read,
and
set-A
commands.
Lastly, parameters can be assigned values using assignment operators
inside arithmetic expressions (see
below) or using the
.Sm off
.Pf ${ Ar name No = Ar value No }
.Sm on
form of the parameter substitution (see below).

Parameters with the export attribute (set using the
export
or
typeset-x
commands, or by parameter assignments followed by simple commands) are put in
the environment (see
environ(7))
of commands run by the shell as
name
pairs.
The order in which parameters appear in the environment of a command is
unspecified.
When the shell starts up, it extracts parameters and their values
from its environment and automatically sets the export attribute for those
parameters.

Modifiers can be applied to the
.Pf ${ Ns Ar name Ns }
form of parameter substitution:

.Sm off

${ name:- word}

.Sm on
If
name
is set and not
NULL,
it is substituted; otherwise,
word
is substituted.
.Sm off

${ name:+ word}

.Sm on
If
name
is set and not
NULL,
word
is substituted; otherwise, nothing is substituted.
.Sm off

${ name:= word}

.Sm on
If
name
is set and not
NULL,
it is substituted; otherwise, it is assigned
word
and the resulting value of
name
is substituted.
.Sm off

${ name:? word}

.Sm on
If
name
is set and not
NULL,
it is substituted; otherwise,
word
is printed on standard error (preceded by
name::)
and an error occurs (normally causing termination of a shell script, function,
or script sourced using the
\&.
built-in).
If
word
is omitted, the string
parameter null or not set
is used instead.

In the above modifiers, the
"\&:"
can be omitted, in which case the conditions only depend on
name
being set (as opposed to set and not
NULL)).
If
word
is needed, parameter, command, arithmetic, and tilde substitution are performed
on it; if
word
is not needed, it is not evaluated.

The following forms of parameter substitution can also be used:

Pf ${#

The number of positional parameters if
name
is
"*",
"@",
or not specified; otherwise the length of the string value of parameter
name.

Pf ${#

Pf ${#

The number of elements in the array
name.

.Sm off

.Pf ${ Ar name
.Pf # Ar pattern No }

.Pf ${ Ar name
.Pf ## Ar pattern No }
.Sm on
If
pattern
matches the beginning of the value of parameter
name,
the matched text is deleted from the result of substitution.
A single
"#"
results in the shortest match, and two
of them result in the longest match.

.Sm off

.Pf ${ Ar name
.Pf % Ar pattern No }

.Pf ${ Ar name
.Pf %% Ar pattern No }
.Sm on
Like ${..#..} substitution, but it deletes from the end of the value.

The following special parameters are implicitly set by the shell and cannot be
set directly using assignments:

\&!

Process ID of the last background process started.
If no background processes have been started, the parameter is not set.

\

The number of positional parameters ($1, $2, etc.).

\&$

The PID of the shell, or the PID of the original shell if it is a subshell.
Do
NOT
use this mechanism for generating temporary file names; see
mktemp(1)
instead.

-

The concatenation of the current single letter options (see the
set
command below for a list of options).

\&?

The exit status of the last non-asynchronous command executed.
If the last command was killed by a signal,
$?\&
is set to 128 plus the signal number.

0

The name of the shell, determined as follows:
the first argument to
ksh
if it was invoked with the
-c
option and arguments were given; otherwise the
file
argument, if it was supplied;
or else the basename the shell was invoked with (i.e.\&
argv[0]).
$0
is also set to the name of the current script or
the name of the current function, if it was defined with the
function
keyword (i.e. a Korn shell style function).

1... 9

The first nine positional parameters that were supplied to the shell, function,
or script sourced using the
\&.
built-in.
Further positional parameters may be accessed using
.Pf ${ Ar number Ns } .

*

All positional parameters (except parameter 0) i.e. $1, $2, $3, ...
If used
outside of double quotes, parameters are separate words (which are subjected
to word splitting); if used within double quotes, parameters are separated
by the first character of the
IFS
parameter (or the empty string if
IFS
is
NULL)).

@

Same as
$*,
unless it is used inside double quotes, in which case a separate word is
generated for each positional parameter.
If there are no positional parameters, no word is generated.
$@
can be used to access arguments, verbatim, without losing
NULL
arguments or splitting arguments with spaces.

The following parameters are set and/or used by the shell:

_(underscore)

When an external command is executed by the shell, this parameter is set in the
environment of the new process to the path of the executed command.
In interactive use, this parameter is also set in the parent shell to the last
word of the previous command.
When
MAILPATH
messages are evaluated, this parameter contains the name of the file that
changed (see the
MAILPATH
parameter, below).

CDPATH

Search path for the
cd
built-in command.
It works the same way as
PATH
for those directories not beginning with
"/"
in
cd
commands.
Note that if
CDPATH
is set and does not contain
\&.
or contains an empty path, the current directory is not searched.
Also, the
cd
built-in command will display the resulting directory when a match is found
in any search path other than the empty path.

COLUMNS

Set to the number of columns on the terminal or window.
Currently set to the
cols
value as reported by
stty(1)
if that value is non-zero.
This parameter is used by the interactive line editing modes, and by the
select,
set-o,
and
kill-l
commands to format information columns.

EDITOR

If the
VISUAL
parameter is not set, this parameter controls the command-line editing mode for
interactive shells.
See the
VISUAL
parameter below for how this works.

Note:
traditionally,
EDITOR
was used to specify the name of an (old-style) line editor, such as
ed(1),
and
VISUAL
was used to specify a (new-style) screen editor, such as
vi(1).
Hence if
VISUAL
is set, it overrides
EDITOR.

ENV

If this parameter is found to be set after any profile files are executed, the
expanded value is used as a shell startup file.
It typically contains function and alias definitions.

ERRNO

Integer value of the shell's
errno
variable.
It indicates the reason the last system call failed.
Not yet implemented.

EXECSHELL

If set, this parameter is assumed to contain the shell that is to be used to
execute commands that
execve(2)
fails to execute and which do not start with a
#! 
sequence.

FCEDIT

The editor used by the
fc
command (see below).

FPATH

Like
PATH,
but used when an undefined function is executed to locate the file defining the
function.
It is also searched when a command can't be found using
PATH.
See
below for more information.

HISTFILE

The name of the file used to store command history.
When assigned to, history is loaded from the specified file.
Also, several invocations of the shell
running on the same machine will share history if their
HISTFILE
parameters all point to the same file.

Note:
If
HISTFILE
isn't set, no history file is used.
This is different from the original Korn shell, which uses
$HOME/.sh_history;
in the future,
pdksh
may also use a default history file.

HISTSIZE

The number of commands normally stored for history.
The default is 500.

HOME

The default directory for the
cd
command and the value substituted for an unqualified
~
(see
below).

IFS

Internal field separator, used during substitution and by the
read
command, to split values into distinct arguments; normally set to space, tab,
and newline.
See
above for details.

Note:
This parameter is not imported from the environment when the shell is
started.

KSH_VERSION

The version of the shell and the date the version was created (read-only).

LINENO

The line number of the function or shell script that is currently being
executed.

LINES

Set to the number of lines on the terminal or window.

MAIL

If set, the user will be informed of the arrival of mail in the named file.
This parameter is ignored if the
MAILPATH
parameter is set.

MAILCHECK

How often, in seconds, the shell will check for mail in the file(s) specified
by
MAIL
or
MAILPATH.
If set to 0, the shell checks before each prompt.
The default is 600 (10 minutes).

MAILPATH

A list of files to be checked for mail.
The list is colon separated, and each file may be followed by a
"\&?"
and a message to be printed if new mail has arrived.
Command, parameter, and
arithmetic substitution is performed on the message, and, during substitution,
the parameter
$_
contains the name of the file.
The default message is
you have mail in $_.

OLDPWD

The previous working directory.
Unset if
cd
has not successfully changed directories since the shell started, or if the
shell doesn't know where it is.

OPTARG

When using
getopts,
it contains the argument for a parsed option, if it requires one.

OPTIND

The index of the next argument to be processed when using
getopts.
Assigning 1 to this parameter causes
getopts
to process arguments from the beginning the next time it is invoked.

PATH

A colon separated list of directories that are searched when looking for
commands and files sourced using the
\&.
command (see below).
An empty string resulting from a leading or trailing
colon, or two adjacent colons, is treated as a
\&.
(the current directory).

POSIXLY_CORRECT

If set, this parameter causes the
posix
option to be enabled.
See
below.

PPID

The process ID of the shell's parent (read-only).

PS1

The primary prompt for interactive shells.
Parameter, command, and arithmetic
substitutions are performed,
and the prompt string can be customised using
backslash-escaped special characters.

Note that since the command-line editors try to figure out how long the prompt
is (so they know how far it is to the edge of the screen), escape codes in
the prompt tend to mess things up.
You can tell the shell not to count certain
sequences (such as escape codes) by using the
\e[
substitution (see below) or by prefixing your prompt with a non-printing
character (such as control-A) followed by a carriage return and then delimiting
the escape codes with this non-printing character.
By the way, don't blame me for
this hack; it's in the original
ksh.

The default prompt is
$\ \&
for non-root users,
#\ \&
for root.
If
ksh
is invoked by root and
PS1
does not contain a
#
character, the default value will be used even if
PS1
already exists in the environment.

The following backslash-escaped special characters can be used
to customise the prompt:

\ea

Insert an ASCII bell character.

\ed

The current date, in the format
Day Month Date
for example
Wed Nov 03.

\eD{

The current date, with
format
converted by
strftime(3).
The braces must be specified.

\ee

Insert an ASCII escape character.

\eh

The hostname, minus domain name.

\eH

The full hostname, including domain name.

\ej

Current number of jobs running
(see
below).

\el

The controlling terminal.

\en

Insert a newline character.

\er

Insert a carriage return character.

\es

The name of the shell.

\et

The current time, in 24-hour HH:MM:SS format.

\eT

The current time, in 12-hour HH:MM:SS format.

\e@

The current time, in 12-hour HH:MM:SS AM/PM format.

\eA

The current time, in 24-hour HH:MM format.

\eu

The current user's username.

\ev

The current version of
ksh.

\eV

Like
\ev,
but more verbose.

\ew

The current working directory.
$HOME
is abbreviated as
~.

\eW

The basename of
the current working directory.

\e!

The current history number.
An unescaped
"!\&"
will produce the current history number too,
as per the POSIX specification.
A literal
"\&!"
can be put in the prompt by placing
""!!
in
PS1.

\e#

The current command number.
This could be different to the current history number,
if
HISTFILE
contains a history list from a previous session.

\e$

The default prompt i.e.\&
# \&
if the effective UID is 0,
otherwise
$ \&.
Since the shell interprets
$
as a special character within double quotes,
it is safer in this case to escape the backslash
than to try quoting it.

\e

The octal character
nnn.

\e\e

Insert a single backslash character.

\e[

Normally the shell keeps track of the number of characters in the prompt.
Use of this sequence turns off that count.

\e]

Use of this sequence turns the count back on.

Note that the backslash itself may be interpreted by the shell.
Hence, to set
PS1
either escape the backslash itself,
or use double quotes.
The latter is more practical:

PS1="\eu "

This is a more complex example,
which does not rely on the above backslash-escaped sequences.
It embeds the current working directory,
in reverse video,
in the prompt string:

Secondary prompt string, by default
\*(Gt\ \&,
used when more input is needed to complete a command.

PS3

Prompt used by the
select
statement when reading a menu selection.
The default is
#?\ \&.

PS4

Used to prefix commands that are printed during execution tracing (see the
set-x
command below).
Parameter, command, and arithmetic substitutions are performed
before it is printed.
The default is
+\ \&.

PWD

The current working directory.
May be unset or
NULL
if the shell doesn't know where it is.

RANDOM

A random number generator.
Every time
RANDOM
is referenced, it is assigned the next random number in the range
0\-32767.
By default,
arc4random(3)
is used to produce values.
If the variable
RANDOM
is assigned a value, the value is used as the seed to
srand(3)
and subsequent references of
RANDOM
will use
rand(3)
to produce values, resulting in a predictable sequence.

REPLY

Default parameter for the
read
command if no names are given.
Also used in
select
loops to store the value that is read from standard input.

SECONDS

The number of seconds since the shell started or, if the parameter has been
assigned an integer value, the number of seconds since the assignment plus the
value that was assigned.

TMOUT

If set to a positive integer in an interactive shell, it specifies the maximum
number of seconds the shell will wait for input after printing the primary
prompt
(PS1).
If the time is exceeded, the shell exits.

TMPDIR

The directory temporary shell files are created in.
If this parameter is not
set, or does not contain the absolute path of a writable directory, temporary
files are created in
/tmp.

VISUAL

If set, this parameter controls the command-line editing mode for interactive
shells.
If the last component of the path specified in this parameter contains
the string
vi,
emacs,
or
gmacs,
the
vi(),
emacs(),
or
gmacs()
(Gosling emacs) editing mode is enabled, respectively.
See also the
EDITOR
parameter, above.

Tilde expansion

Tilde expansion, which is done in parallel with parameter substitution, is done
on words starting with an unquoted
"~".
The characters following the tilde, up to the first
"/",
if any, are assumed to be a login name.
If the login name is empty,
"+",
or
"-",
the value of the
HOME,
PWD,
or
OLDPWD
parameter is substituted, respectively.
Otherwise, the password file is
searched for the login name, and the tilde expression is substituted with the
user's home directory.
If the login name is not found in the password file or
if any quoting or parameter substitution occurs in the login name, no
substitution is performed.

In parameter assignments
(such as those preceding a simple-command or those occurring
in the arguments of
alias,
export,
readonly,
and
typeset)),
tilde expansion is done after any assignment
(i.e. after the equals sign)
or after an unquoted colon
(\&:);
login names are also delimited by colons.

The home directory of previously expanded login names are cached and re-used.
The
alias-d
command may be used to list, change, and add to this cache (e.g.\&
alias-d fac=/usr/local/facilities; cd ~fac/bin).

Brace expansion (alteration)

Brace expressions take the following form:
.Sm off
prefix{ str1,...,
strN} suffix
.Sm on

The expressions are expanded to
N
words, each of which is the concatenation of
prefix,
str,
and
suffix
(e.g.\&
a{c,b{X,Y},d}e
expands to four words:
ace,
abXe,
abYe,
and
ade).
As noted in the example, brace expressions can be nested and the resulting
words are not sorted.
Brace expressions must contain an unquoted comma
(\&,)
for expansion to occur (e.g.\&
{}
and
{foo}
are not expanded).
Brace expansion is carried out after parameter substitution
and before file name generation.

File name patterns

A file name pattern is a word containing one or more unquoted
"\&?",
"*",
"+",
"@",
or
"\&!"
characters or
[..]
sequences.
Once brace expansion has been performed, the shell replaces file
name patterns with the sorted names of all the files that match the pattern
(if no files match, the word is left unchanged).
The pattern elements have the following meaning:

\&?

Matches any single character.

\&*

Matches any sequence of characters.

[..][..]

Matches any of the characters inside the brackets.
Ranges of characters can be
specified by separating two characters by a
"-"
(e.g.\&
[a0-9]
matches the letter
a
or any digit).
In order to represent itself, a
"-"
must either be quoted or the first or last character in the character list.
Similarly, a
"\&]"
must be quoted or the first character in the list if it is to represent itself
instead of the end of the list.
Also, a
"\&!"
appearing at the start of the list has special meaning (see below), so to
represent itself it must be quoted or appear later in the list.

Within a bracket expression, the name of a
character class
enclosed in
[:
and
:]
stands for the list of all characters belonging to that class.
Supported character classes:

alnum

cntrl

lower

space

alpha

digit

print

upper

blank

graph

punct

xdigit

These match characters using the macros specified in
ctype(3).
A character class may not be used as an endpoint of a range.

[!..][!..]

Like [..],
except it matches any character not inside the brackets.
.Sm off

*( pattern\*(Ba...\*(Ba pattern)

.Sm on
Matches any string of characters that matches zero or more occurrences of the
specified patterns.
Example: The pattern
*(foo|bar)
matches the strings
,
foo,
bar,
foobarfoo,
etc.
.Sm off

+( pattern\*(Ba...\*(Ba pattern)

.Sm on
Matches any string of characters that matches one or more occurrences of the
specified patterns.
Example: The pattern
+(foo|bar)
matches the strings
foo,
bar,
foobar,
etc.
.Sm off

?( pattern\*(Ba...\*(Ba pattern)

.Sm on
Matches the empty string or a string that matches one of the specified
patterns.
Example: The pattern
?(foo|bar)
only matches the strings
,
foo,
and
bar.
.Sm off

@( pattern\*(Ba...\*(Ba pattern)

.Sm on
Matches a string that matches one of the specified patterns.
Example: The pattern
@(foo|bar)
only matches the strings
foo
and
bar.
.Sm off

!( pattern\*(Ba...\*(Ba pattern)

.Sm on
Matches any string that does not match one of the specified patterns.
Examples: The pattern
!(foo|bar)
matches all strings except
foo
and
bar;
the pattern
!(*)
matches no strings; the pattern
!(?)*\&
matches all strings (think about it).

Note that
pdksh
currently never matches
\&.
and
....,
but the original
ksh(),
Bourne
sh(),
and bash do, so this may have to change (too bad).

Note that none of the above pattern elements match either a period
(\&.)
at the start of a file name or a slash
(/),
even if they are explicitly used in a [..] sequence; also, the names
\&.
and
..
are never matched, even by the pattern
.*.

If the
markdirs
option is set, any directories that result from file name generation are marked
with a trailing
"/".

Input/output redirection

When a command is executed, its standard input, standard output, and standard
error (file descriptors 0, 1, and 2, respectively) are normally inherited from
the shell.
Three exceptions to this are commands in pipelines, for which
standard input and/or standard output are those set up by the pipeline,
asynchronous commands created when job control is disabled, for which standard
input is initially set to be from
/dev/null,
and commands for which any of the following redirections have been specified:

\*(Gt file

Standard output is redirected to
file.
If
file
does not exist, it is created; if it does exist, is a regular file, and the
noclobber
option is set, an error occurs; otherwise, the file is truncated.
Note that this means the command
cmd\*(Lt foo \*(Gt foo
will open
foo
for reading and then truncate it when it opens it for writing, before
cmd
gets a chance to actually read
foo.

\*(Gt\*(Ba file

Same as
\*(Gt,
except the file is truncated, even if the
noclobber
option is set.

\*(Gt\*(Gt file

Same as
\*(Gt,
except if
file
exists it is appended to instead of being truncated.
Also, the file is opened
in append mode, so writes always go to the end of the file (see
open(2/)).

\*(Lt file

Standard input is redirected from
file,
which is opened for reading.

\*(Lt\*(Gt file

Same as
\*(Lt,
except the file is opened for reading and writing.

\*(Lt\*(Lt marker

After reading the command line containing this kind of redirection (called a
here document),
the shell copies lines from the command source into a temporary file until a
line matching
marker
is read.
When the command is executed, standard input is redirected from the
temporary file.
If
marker
contains no quoted characters, the contents of the temporary file are processed
as if enclosed in double quotes each time the command is executed, so
parameter, command, and arithmetic substitutions are performed, along with
backslash
(\e)
escapes for
"$",
"`",
"\e",
and
"\enewline".
If multiple here documents are used on the same command line, they are saved in
order.

\*(Lt\*(Lt- marker

Same as
\*(Lt\*(Lt,
except leading tabs are stripped from lines in the here document.

\*(Lt& fd

Standard input is duplicated from file descriptor
fd.
fd
can be a single digit, indicating the number of an existing file descriptor;
the letter
"p",
indicating the file descriptor associated with the output of the current
co-process; or the character
"-",
indicating standard input is to be closed.

\*(Gt& fd

Same as
\*(Lt&,
except the operation is done on standard output.

In any of the above redirections, the file descriptor that is redirected
(i.e. standard input or standard output)
can be explicitly given by preceding the
redirection with a single digit.
Parameter, command, and arithmetic
substitutions, tilde substitutions, and (if the shell is interactive)
file name generation are all performed on the
file,
marker,
and
fd
arguments of redirections.
Note, however, that the results of any file name
generation are only used if a single file is matched; if multiple files match,
the word with the expanded file name generation characters is used.
Note
that in restricted shells, redirections which can create files cannot be used.

For simple-commands, redirections may appear anywhere in the command; for
compound-commands
(
if
statements, etc.
),
any redirections must appear at the end.
Redirections are processed after
pipelines are created and in the order they are given, so the following
will print an error with a line number prepended to it:

$ cat /foo/bar 2\*(Gt&1 \*(Gt /dev/null \*(Ba cat -n

Arithmetic expressions

Integer arithmetic expressions can be used with the
let
command, inside $((..)) expressions, inside array references (e.g.\&
name,
as numeric arguments to the
test
command, and as the value of an assignment to an integer parameter.

Expressions may contain alpha-numeric parameter identifiers, array references,
and integer constants and may be combined with the following C operators
(listed and grouped in increasing order of precedence):

Integer constants may be specified with arbitrary bases using the notation
base,
where
base
is a decimal integer specifying the base, and
number
is a number in the specified base.
Additionally,
integers may be prefixed with
֪X
or
֪x
(specifying base 16)
or
֪
(base 8)
in all forms of arithmetic expressions,
except as numeric arguments to the
test
command.

The operators are evaluated as follows:

unary +

Result is the argument (included for completeness).

unary -

Negation.

\&!

Logical NOT;
the result is 1 if argument is zero, 0 if not.

~

Arithmetic (bit-wise) NOT.

++

Increment; must be applied to a parameter (not a literal or other expression).
The parameter is incremented by 1.
When used as a prefix operator, the result
is the incremented value of the parameter; when used as a postfix operator, the
result is the original value of the parameter.

--

Similar to
++,
except the parameter is decremented by 1.

\&,

Separates two arithmetic expressions; the left-hand side is evaluated first,
then the right.
The result is the value of the expression on the right-hand side.

=

Assignment; the variable on the left is set to the value on the right.

Logical OR;
the result is 1 if either argument is non-zero, 0 if not.
The right argument is evaluated only if the left argument is zero.

&&

Logical AND;
the result is 1 if both arguments are non-zero, 0 if not.
The right argument is evaluated only if the left argument is non-zero.

\*(Ba

Arithmetic (bit-wise) OR.

^

Arithmetic (bit-wise) XOR
(exclusive-OR).

&

Arithmetic (bit-wise) AND.

==

Equal; the result is 1 if both arguments are equal, 0 if not.

!=

Not equal; the result is 0 if both arguments are equal, 1 if not.

\*(Lt

Less than; the result is 1 if the left argument is less than the right, 0 if
not.

\*(Lt= \*(Gt= \*(Gt

Less than or equal, greater than or equal, greater than.
See
\*(Lt.

\*(Lt\*(Lt \*(Gt\*(Gt

Shift left (right); the result is the left argument with its bits shifted left
(right) by the amount given in the right argument.

+ - * /

Addition, subtraction, multiplication, and division.

%

Remainder; the result is the remainder of the division of the left argument by
the right.
The sign of the result is unspecified if either argument is negative.

.Sm off
arg1?
arg2:
arg3
.Sm on
If
arg1
is non-zero, the result is
arg2;
otherwise the result is
arg3.

Co-processes

A co-process, which is a pipeline created with the
\*(Ba&
operator, is an asynchronous process that the shell can both write to (using
print-p)
and read from (using
read-p).
The input and output of the co-process can also be manipulated using
\*(Gt&p
and
\*(Lt&p
redirections, respectively.
Once a co-process has been started, another can't
be started until the co-process exits, or until the co-process's input has been
redirected using an
execn
redirection.
If a co-process's input is redirected in this way, the next
co-process to be started will share the output with the first co-process,
unless the output of the initial co-process has been redirected using an
execn
redirection.

Some notes concerning co-processes:

The only way to close the co-process's input (so the co-process reads an
end-of-file) is to redirect the input to a numbered file descriptor and then
close that file descriptor e.g.\&
exec3\*(Gt&p; exec 3\*(Gt&-.

In order for co-processes to share a common output, the shell must keep the
write portion of the output pipe open.
This means that end-of-file will not be
detected until all co-processes sharing the co-process's output have exited
(when they all exit, the shell closes its copy of the pipe).
This can be
avoided by redirecting the output to a numbered file descriptor (as this also
causes the shell to close its copy).
Note that this behaviour is slightly
different from the original Korn shell which closes its copy of the write
portion of the co-process output when the most recently started co-process
(instead of when all sharing co-processes) exits.

print-p
will ignore
SIGPIPE
signals during writes if the signal is not being trapped or ignored; the same
is true if the co-process input has been duplicated to another file descriptor
and
print-u
is used.

Functions

Functions are defined using either Korn shell
functionfunction-name
syntax or the Bourne/POSIX shell
function-name()
syntax (see below for the difference between the two forms).
Functions are like
.-scripts
(i.e. scripts sourced using the
\&.
built-in)
in that they are executed in the current environment.
However, unlike
.-scripts,
shell arguments (i.e. positional parameters $1, $2, etc.)\&
are never visible inside them.
When the shell is determining the location of a command, functions
are searched after special built-in commands, before regular and
non-regular built-ins, and before the
PATH
is searched.

An existing function may be deleted using
unset-f function-name.
A list of functions can be obtained using
typeset+f
and the function definitions can be listed using
typeset-f.
The
autoload
command (which is an alias for
typeset-fu)
may be used to create undefined functions: when an undefined function is
executed, the shell searches the path specified in the
FPATH
parameter for a file with the same name as the function, which, if found, is
read and executed.
If after executing the file the named function is found to
be defined, the function is executed; otherwise, the normal command search is
continued (i.e. the shell searches the regular built-in command table and
PATH)).
Note that if a command is not found using
PATH,
an attempt is made to autoload a function using
FPATH
(this is an undocumented feature of the original Korn shell).

Functions can have two attributes,
trace
and
export,
which can be set with
typeset-ft
and
typeset-fx,
respectively.
When a traced function is executed, the shell's
xtrace
option is turned on for the function's duration; otherwise, the
xtrace
option is turned off.
The
export
attribute of functions is currently not used.
In the original Korn shell,
exported functions are visible to shell scripts that are executed.

Since functions are executed in the current shell environment, parameter
assignments made inside functions are visible after the function completes.
If this is not the desired effect, the
typeset
command can be used inside a function to create a local parameter.
Note that special parameters (e.g.\&
\&$$, $!)
can't be scoped in this way.

The exit status of a function is that of the last command executed in the
function.
A function can be made to finish immediately using the
return
command; this may also be used to explicitly specify the exit status.

Functions defined with the
function
reserved word are treated differently in the following ways from functions
defined with the
()
notation:

The $0 parameter is set to the name of the function
(Bourne-style functions leave $0 untouched).

OPTIND
is saved/reset and restored on entry and exit from the function so
getopts
can be used properly both inside and outside the function (Bourne-style
functions leave
OPTIND
untouched, so using
getopts
inside a function interferes with using
getopts
outside the function).

In the future, the following differences will also be added:

A separate trap/signal environment will be used during the execution of
functions.
This will mean that traps set inside a function will not affect the
shell's traps and signals that are not ignored in the shell (but may be
trapped) will have their default effect in a function.

The EXIT trap, if set in a function, will be executed after the function
returns.

POSIX mode

The shell is intended to be POSIX compliant;
however, in some cases, POSIX behaviour is contrary either to
the original Korn shell behaviour or to user convenience.
How the shell behaves in these cases is determined by the state of the
posix
option
(set-o posix).
If it is on, the POSIX behaviour is followed; otherwise, it is not.
The
posix
option is set automatically when the shell starts up if the environment
contains the
POSIXLY_CORRECT
parameter.
The shell can also be compiled so that it is in POSIX mode by default;
however, this is usually not desirable.

The following is a list of things that are affected by the state of the
posix
option:

Occurrences of
\e\&"
inside double quoted
`..`
command substitutions.
In POSIX mode, the
\e\&"
is interpreted when the command is interpreted;
in non-POSIX mode,
the backslash is stripped before the command substitution is interpreted.
For example,
echo\&"`echo \e\&"hi\e\&"`\&"
produces
\&"hi\&"
in POSIX mode,
hi
in non-POSIX mode.
To avoid problems, use the
$(...)\&
form of command substitution.

kill-l
output.
In POSIX mode, only signal names are listed (in a single line);
in non-POSIX mode,
signal numbers, names, and descriptions are printed (in columns).
In the future, a new option
(-v perhaps)
will be added to distinguish the two behaviours.

echo
options.
In POSIX mode,
-e
and
-E
are not treated as options, but printed like other arguments;
in non-POSIX mode, these options control the interpretation
of backslash sequences.

fg
exit status.
In POSIX mode, the exit status is 0 if no errors occur;
in non-POSIX mode, the exit status is that of the last foregrounded job.

eval
exit status.
If
eval
gets to see an empty command (i.e.\&
eval`false`),
its exit status in POSIX mode will be 0.
In non-POSIX mode,
it will be the exit status of the last command substitution that was
done in the processing of the arguments to
eval
(or 0 if there were no command substitutions).

getopts.
In POSIX mode, options must start with a
"-";
in non-POSIX mode, options can start with either
"-"
or
"+".

Brace expansion (also known as alternation).
In POSIX mode, brace expansion is disabled;
in non-POSIX mode, brace expansion is enabled.
Note that
set-o posix
(or setting the
POSIXLY_CORRECT
parameter) automatically turns the
braceexpand
option off; however, it can be explicitly turned on later.

set-.
In POSIX mode, this does not clear the
verbose
or
xtrace
options; in non-POSIX mode, it does.

set
exit status.
In POSIX mode, the exit status of
set
is 0 if there are no errors;
in non-POSIX mode, the exit status is that of any
command substitutions performed in generating the
set
command.
For example,
set-- `false`; echo $?\&
prints 0 in POSIX mode, 1 in non-POSIX mode.
This construct is used in most shell scripts that use the old
getopt(1)
command.

Alias expansion.
In POSIX mode, alias expansion is only carried out when reading command words;
in non-POSIX mode, alias expansion is carried out on any
word following an alias that ended in a space.
For example, the following
for
loop uses parameter
i
in POSIX mode and
j
in non-POSIX mode:

alias a='for ' i='j'
a i in 1 2; do echo i=$i j=$j; done

test.
In POSIX mode, the expression
-t
(preceded by some number of
\&!
arguments) is always true as it is a non-zero length string;
in non-POSIX mode, it tests if file descriptor 1 is a
tty(4)
(i.e. the
fd
argument to the
-t
test may be left out and defaults to 1).

Strict Bourne shell mode

When the
sh
option is enabled (see the
set
command),
ksh
will behave like
sh(1)
in the following ways:

The parameter
$_
is not set to:

the expanded alias' full program path after entering commands
that are tracked aliases

the last argument on the command line after entering external
commands

the file that changed when
MAILPATH
is set to monitor a mailbox

File descriptors are left untouched when executing
exec
with no arguments.

Backslash-escaped special characters are not substituted in
PS1.

Sequences of
((...))
are not interpreted as arithmetic expressions.

Command execution

After evaluation of command-line arguments, redirections, and parameter
assignments, the type of command is determined: a special built-in, a
function, a regular built-in, or the name of a file to execute found using the
PATH
parameter.
The checks are made in the above order.
Special built-in commands differ from other commands in that the
PATH
parameter is not used to find them, an error during their execution can
cause a non-interactive shell to exit, and parameter assignments that are
specified before the command are kept after the command completes.
Just to confuse things, if the
posix
option is turned off (see the
set
command below), some special commands are very special in that no field
splitting, file globbing, brace expansion, nor tilde expansion is performed
on arguments that look like assignments.
Regular built-in commands are different only in that the
PATH
parameter is not used to find them.

The original
ksh
and POSIX differ somewhat in which commands are considered
special or regular:

In the future, the additional
ksh
special and regular commands may be treated
differently from the POSIX special and regular commands.

Once the type of command has been determined, any command-line parameter
assignments are performed and exported for the duration of the command.

The following describes the special and regular built-in commands:

\&.file[arg]...

Execute the commands in
file
in the current environment.
The file is searched for in the directories of
PATH.
If arguments are given, the positional parameters may be used to access them
while
file
is being executed.
If no arguments are given, the positional parameters are
those of the environment the command is used in.

\&:[]...

The null command.
Exit status is set to zero.

.Oo Fl d \*(Ba t Oo Fl r Oc \*(Ba
-+-xOc
[-p]
[-+]
.Oo Ar name
[]
...Oc
Without arguments,
alias
lists all aliases.
For any name without a value, the existing alias is listed.
Any name with a value defines an alias (see
above).

When listing aliases, one of two formats is used.
Normally, aliases are listed as
name,
where
value
is quoted.
If options were preceded with
"+",
or a lone
"+"
is given on the command line, only
name
is printed.

The
-d
option causes directory aliases, which are used in tilde expansion, to be
listed or set (see
above).

If the
-p
option is used, each alias is prefixed with the string
alias\ \&.

The
-t
option indicates that tracked aliases are to be listed/set (values specified on
the command line are ignored for tracked aliases).
The
-r
option indicates that all tracked aliases are to be reset.

The
-x
option sets
(+xclears)
the export attribute of an alias, or, if no names are given, lists the aliases
with the export attribute (exporting an alias has no effect).

bg[job]...

Resume the specified stopped job(s) in the background.
If no jobs are specified,
%+
is assumed.
See
below for more information.

bind[-l]

The current bindings are listed.
If the
-l
flag is given,
bind
instead lists the names of the functions to which keys may be bound.
See
for more information.

string...

string...
The specified editing command is bound to the given
string,
which should consist of a control character
optionally preceded by one of the two prefix characters.
Future input of the
string
will cause the editing command to be immediately invoked.
If the
-m
flag is given, the specified input
string
will afterwards be immediately replaced by the given
substitute
string, which may contain editing commands.

Control characters may be written using caret notation
i.e. ^X represents Control-X.
Note that although only two prefix characters (usually ESC and ^X)
are supported, some multi-character sequences can be supported.

The following default bindings show how the arrow keys
on an ANSI terminal or xterm are bound
(of course some escape sequences won't work out quite this nicely):

cd
[-LP]
[dir]
Set the working directory to
dir.
If the parameter
CDPATH
is set, it lists the search path for the directory containing
dir.
A
NULL
path means the current directory.
If
dir
is found in any component of the
CDPATH
search path other than the
NULL
path, the name of the new working directory will be written to standard output.
If
dir
is missing, the home directory
HOME
is used.
If
dir
is
"-",
the previous working directory is used (see the
OLDPWD
parameter).

If the
-L
option (logical path) is used or if the
physical
option isn't set (see the
set
command below), references to
..
in
dir
are relative to the path used to get to the directory.
If the
-P
option (physical path) is used or if the
physical
option is set,
..
is relative to the filesystem directory tree.
The
PWD
and
OLDPWD
parameters are updated to reflect the current and old working directory,
respectively.

cd
[-LP]
oldnew
The string
new
is substituted for
old
in the current directory, and the shell attempts to change to the new
directory.

command
[-pVv]
cmd
[arg]...
If neither the
-v
nor
-V
option is given,
cmd
is executed exactly as if
command
had not been specified, with two exceptions:
firstly,
cmd
cannot be a shell function;
and secondly, special built-in commands lose their specialness
(i.e. redirection and utility errors do not cause the shell to
exit, and command assignments are not permanent).

If the
-p
option is given, a default search path is used instead of the current value of
PATH
(the actual value of the default path is system dependent: on
POSIX-ish systems, it is the value returned by
getconfCS_PATH).

If the
-v
option is given, instead of executing
cmd,
information about what would be executed is given (and the same is done for
arg...).
For special and regular built-in commands and functions, their names are simply
printed; for aliases, a command that defines them is printed; and for commands
found by searching the
PATH
parameter, the full path of the command is printed.
If no command is found
(i.e. the path search fails), nothing is printed and
command
exits with a non-zero status.
The
-V
option is like the
-v
option, except it is more verbose.

continue[level]

Jumps to the beginning of the
level
inner-most
for,
select,
until,
or
while
loop.
level
defaults to 1.

echo
[-Een]
[arg]...
Prints its arguments (separated by spaces) followed by a newline, to the
standard output.
The newline is suppressed if any of the arguments contain the
backslash sequence
"\ec".
See the
print
command below for a list of other backslash sequences that are recognized.

The options are provided for compatibility with
BSD
shell scripts.
The
-n
option suppresses the trailing newline,
-e
enables backslash interpretation (a no-op, since this is normally done), and
-E
suppresses backslash interpretation.
If the
posix
option is set, only the first argument is treated as an option, and only
if it is exactly
-n.

evalcommand...

The arguments are concatenated (with spaces between them) to form a single
string which the shell then parses and executes in the current environment.

exec
[command[arg]]...
The command is executed without forking, replacing the shell process.

If no command is given except for I/O redirection, the I/O redirection is
permanent and the shell is
not replaced.
Any file descriptors greater than 2 which are opened or
dup(2/Ns)
in this way are not made available to other executed commands (i.e. commands
that are not built-in to the shell).
Note that the Bourne shell differs here;
it does pass these file descriptors on.

exit[status]

The shell exits with the specified exit status.
If
status
is not specified, the exit status is the current value of the
$?\&
parameter.

export
[-p]
[parameter]
Sets the export attribute of the named parameters.
Exported parameters are passed in the environment to executed commands.
If values are specified, the named parameters are also assigned.

If no parameters are specified, the names of all parameters with the export
attribute are printed one per line, unless the
-p
option is used, in which case
export
commands defining all exported parameters, including their values, are printed.

false

A command that exits with a non-zero status.

fc
.Oo Fl e Ar editor \*(Ba
-l [-n Oc]
[-r]
[first[last]]
first
and
last
select commands from the history.
Commands can be selected by history number
or a string specifying the most recent command starting with that string.
The
-l
option lists the command on standard output, and
-n
inhibits the default command numbers.
The
-r
option reverses the order of the list.
Without
-l,
the selected commands are edited by the editor specified with the
-e
option, or if no
-e
is specified, the editor specified by the
FCEDIT
parameter (if this parameter is not set,
/bin/ed
is used), and then executed by the shell.

fc--e- \*(Ba -s
[-g]
[old]
[prefix]
Re-execute the selected command (the previous command by default) after
performing the optional substitution of
old
with
new.
If
-g
is specified, all occurrences of
old
are replaced with
new.
The meaning of
--e-
and
-s
is identical: re-execute the selected command without invoking an editor.
This command is usually accessed with the predefined
aliasr='fc -e -'.

fg[job]...

Resume the specified job(s) in the foreground.
If no jobs are specified,
%+
is assumed.
See
below for more information.

getoptsoptstringname
[arg]...
Used by shell procedures to parse the specified arguments (or positional
parameters, if no arguments are given) and to check for legal options.
optstring
contains the option letters that
getopts
is to recognize.
If a letter is followed by a colon, the option is expected to
have an argument.
Options that do not take arguments may be grouped in a single argument.
If an option takes an argument and the option character is not the
last character of the argument it is found in, the remainder of the argument is
taken to be the option's argument; otherwise, the next argument is the option's
argument.

Each time
getopts
is invoked, it places the next option in the shell parameter
name
and the index of the argument to be processed by the next call to
getopts
in the shell parameter
OPTIND.
If the option was introduced with a
"+",
the option placed in
name
is prefixed with a
"+".
When an option requires an argument,
getopts
places it in the shell parameter
OPTARG.

When an illegal option or a missing option argument is encountered, a question
mark or a colon is placed in
name
(indicating an illegal option or missing argument, respectively) and
OPTARG
is set to the option character that caused the problem.
Furthermore, if
optstring
does not begin with a colon, a question mark is placed in
name,
OPTARG
is unset, and an error message is printed to standard error.

When the end of the options is encountered,
getopts
exits with a non-zero exit status.
Options end at the first (non-option
argument) argument that does not start with a
"-",
or when a
"--"
argument is encountered.

Option parsing can be reset by setting
OPTIND
to 1 (this is done automatically whenever the shell or a shell procedure is
invoked).

Warning: Changing the value of the shell parameter
OPTIND
to a value other than 1, or parsing different sets of arguments without
resetting
OPTIND,
may lead to unexpected results.

hash
[-r]
[name]...
Without arguments, any hashed executable command pathnames are listed.
The
-r
option causes all hashed commands to be removed from the hash table.
Each
name
is searched as if it were a command name and added to the hash table if it is
an executable command.

jobs
[-lnp]
[job]...
Display information about the specified job(s); if no jobs are specified, all
jobs are displayed.
The
-n
option causes information to be displayed only for jobs that have changed
state since the last notification.
If the
-l
option is used, the process ID of each process in a job is also listed.
The
-p
option causes only the process group of each job to be printed.
See
below for the format of
job
and the displayed job.

kill
.Oo Fl s Ar signame \*(Ba
-
-
{ job\*(Ba pid \*(Ba pgrp }
...
Send the specified signal to the specified jobs, process IDs, or process
groups.
If no signal is specified, the
TERM
signal is sent.
If a job is specified, the signal is sent to the job's process group.
See
below for the format of
job.

kill
-l
[exit-status]...
Print the signal name corresponding to
exit-status.
If no arguments are specified, a list of all the signals, their numbers, and
a short description of them are printed.

let[expression]...

Each expression is evaluated (see
above).
If all expressions are successfully evaluated, the exit status is 0 (1)
if the last expression evaluated to non-zero (zero).
If an error occurs during
the parsing or evaluation of an expression, the exit status is greater than 1.
Since expressions may need to be quoted,
(( expr))
is syntactic sugar for
let \&" .

mknod
[-m mode]
name
[-b| -c]
majorminor

mknod
[-m mode]
name-p
Create a device special file.
The file type may be
-b
(block type device),
-c
(character type device),
or
-p
(named pipe).
The file created may be modified according to its
mode
(via the
-m
option),
major
(major device number),
and
minor
(minor device number).

print
.Oo Fl nprsu Ns Oo Ar n Oc \*(Ba
-R [-en Oc]
[argument]...
print
prints its arguments on the standard output, separated by spaces and
terminated with a newline.
The
-n
option suppresses the newline.
By default, certain C escapes are translated.
These include
"\eb",
"\ef",
"\en",
"\er",
"\et",
"\ev",
and
"\e0###"
(
"#"
is an octal digit, of which there may be 0 to 3
).
"\ec"
is equivalent to using the
-n
option.
"\e"
expansion may be inhibited with the
-r
option.
The
-s
option prints to the history file instead of standard output; the
-u
option prints to file descriptor
n
(
n
defaults to 1 if omitted
);
and the
-p
option prints to the co-process (see
above).

The
-R
option is used to emulate, to some degree, the
BSDecho(1)
command, which does not process
"\e"
sequences unless the
-e
option is given.
As above, the
-n
option suppresses the trailing newline.

pwd[-LP]

Print the present working directory.
If the
-L
option is used or if the
physical
option isn't set (see the
set
command below), the logical path is printed (i.e. the path used to
cd
to the current directory).
If the
-P
option (physical path) is used or if the
physical
option is set, the path determined from the filesystem (by following
..
directories to the root directory) is printed.

read
[-prsu ]
[parameter]...
Reads a line of input from the standard input, separates the line into fields
using the
IFS
parameter (see
above), and assigns each field to the specified parameters.
If there are more parameters than fields, the extra parameters are set to
NULL,
or alternatively, if there are more fields than parameters, the last parameter
is assigned the remaining fields (inclusive of any separating spaces).
If no parameters are specified, the
REPLY
parameter is used.
If the input line ends in a backslash and the
-r
option was not used, the backslash and the newline are stripped and more input
is read.
If no input is read,
read
exits with a non-zero status.

The first parameter may have a question mark and a string appended to it, in
which case the string is used as a prompt (printed to standard error before
any input is read) if the input is a
tty(4)
(e.g.\&
readnfoo?'number of foos: ').

The
-u
and
-p
options cause input to be read from file descriptor
n
.Pf ( Ar n
defaults to 0 if omitted)
or the current co-process (see
above for comments on this), respectively.
If the
-s
option is used, input is saved to the history file.

readonly
[-p]
.Oo Ar parameter
[]
...Oc
Sets the read-only attribute of the named parameters.
If values are given,
parameters are set to them before setting the attribute.
Once a parameter is
made read-only, it cannot be unset and its value cannot be changed.

If no parameters are specified, the names of all parameters with the read-only
attribute are printed one per line, unless the
-p
option is used, in which case
readonly
commands defining all read-only parameters, including their values, are
printed.

return[status]

Returns from a function or
.\&
script, with exit status
status.
If no
status
is given, the exit status of the last executed command is used.
If used outside of a function or
.\&
script, it has the same effect as
exit.
Note that
pdksh
treats both profile and
ENV
files as
.\&
scripts, while the original Korn shell only treats profiles as
.\&
scripts.

set[+-abCefhkmnpsuvXx]
[+-ooption]
[+-Aname]
[--]
[arg]...
The
set
command can be used to set
(-)
or clear
(+)
shell options, set the positional parameters, or set an array parameter.
Options can be changed using the
-+-ooption
syntax, where
option
is the long name of an option, or using the
-+-
syntax, where
letter
is the option's single letter name (not all options have a single letter name).
The following table lists both option letters (if they exist) and long names
along with a description of what the option does:

-A name

Sets the elements of the array parameter
name
to
arg...
If
-A
is used, the array is reset (i.e. emptied) first; if
+A
is used, the first N elements are set (where N is the number of arguments);
the rest are left untouched.

-a \*(Ba allexport

All new parameters are created with the export attribute.

-b \*(Ba notify

Print job notification messages asynchronously, instead of just before the
prompt.
Only used if job control is enabled
(-m).

-C \*(Ba noclobber

Prevent \*(Gt redirection from overwriting existing files.
Instead, \*(Gt\*(Ba must be used to force an overwrite.

-e \*(Ba errexit

Exit (after executing the
ERR
trap) as soon as an error occurs or a command fails (i.e. exits with a
non-zero status).
This does not apply to commands whose exit status is
explicitly tested by a shell construct such as
if,
until,
while,
&&,
||,
or
!\&
statements.

Do not execute any commands.
Useful for checking the syntax of scripts
(ignored if interactive).

-p \*(Ba privileged

The shell is a privileged shell.
It is set automatically if, when the shell starts,
the real UID or GID does not match
the effective UID (EUID) or GID (EGID), respectively.
See above for a description of what this means.

-s \*(Ba stdin

If used when the shell is invoked, commands are read from standard input.
Set automatically if the shell is invoked with no arguments.

When
-s
is used with the
set
command it causes the specified arguments to be sorted before assigning them to
the positional parameters (or to array
name,
if
-A
is used).

-u \*(Ba nounset

Referencing of an unset parameter is treated as an error, unless one of the
"-",
"+",
or
"="
modifiers is used.

-v \*(Ba verbose

Write shell input to standard error as it is read.

-X \*(Ba markdirs

Mark directories with a trailing
"/"
during file name generation.

-x \*(Ba xtrace

Print commands and parameter assignments when they are executed, preceded by
the value of
PS4.

bgnice

Background jobs are run with lower priority.

braceexpand

Enable brace expansion (a.k.a. alternation).

csh-history

Enables a subset of
csh(1/Ns)
history editing using the
"!\&"
character.

The shell will not (easily) exit when end-of-file is read;
exit
must be used.
To avoid infinite loops, the shell will exit if
EOF
is read 13 times in a row.

interactive

The shell is an interactive shell.
This option can only be used when the shell is invoked.
See above for a description of what this means.

login

The shell is a login shell.
This option can only be used when the shell is invoked.
See above for a description of what this means.

nohup

Do not kill running jobs with a
SIGHUP
signal when a login shell exits.
Currently set by default, but this will
change in the future to be compatible with the original Korn shell (which
doesn't have this option, but does send the
SIGHUP
signal).

nolog

No effect.
In the original Korn shell, this prevents function definitions from
being stored in the history file.

physical

Causes the
cd
and
pwd
commands to use
physical
(i.e. the filesystem's)
..
directories instead of
logical
directories (i.e. the shell handles
....,
which allows the user to be oblivious of symbolic links to directories).
Clear by default.
Note that setting this option does not affect the current value of the
PWD
parameter; only the
cd
command changes
PWD.
See the
cd
and
pwd
commands above for more details.

posix

Enable POSIX mode.
See
above.

restricted

The shell is a restricted shell.
This option can only be used when the shell is invoked.
See above for a description of what this means.

In vi command-line editing, do command and file name completion when escape
(^[) is entered in command mode.

vi-show8

Prefix characters with the eighth bit set with
M-.
If this option is not set, characters in the range 128\-160 are printed as is,
which may cause problems.

vi-tabcomplete

In vi command-line editing, do command and file name completion when tab (^I)
is entered in insert mode.
This is the default.

viraw

No effect.
In the original Korn shell, unless
viraw
was set, the vi command-line mode would let the
tty(4)
driver do the work until ESC (^[) was entered.
pdksh
is always in viraw mode.

These options can also be used upon invocation of the shell.
The current set of
options (with single letter names) can be found in the parameter
$-.
set-o
with no option name will list all the options and whether each is on or off;
set+o
will print the long names of all options that are currently on.

Remaining arguments, if any, are positional parameters and are assigned, in
order, to the positional parameters (i.e. $1, $2, etc.).
If options end with
"--"
and there are no remaining arguments, all positional parameters are cleared.
If no options or arguments are given, the values of all names are printed.
For unknown historical reasons, a lone
"-"
option is treated specially \- it clears both the
-x
and
-v
options.

shift[number]

The positional parameters
number,
number,
etc. are renamed to
֫,
֬,
etc.
number
defaults to 1.

testexpression

\&[expression\&]

test
evaluates the
expression
and returns zero status if true, 1 if false, or greater than 1 if there
was an error.
It is normally used as the condition command of
if
and
while
statements.
Symbolic links are followed for all
file
expressions except
-h
and
-L.

Shell
option
is set (see the
set
command above for a list of options).
As a non-standard extension, if the option starts with a
"\&!",
the test is negated; the test always fails if
option
doesn't exist (so [ -o foo -o -o !foo ] returns true if and only if option
foo
exists).

On operating systems not supporting
/dev/fd/
devices (where
n
is a file descriptor number), the
test
command will attempt to fake it for all tests that operate on files (except the
-e
test).
For example,
[ -w /dev/fd/2 ] tests if file descriptor 2 is writable.

Note that some special rules are applied (courtesy of POSIX)
if the number of
arguments to
test
or
\&[... \&]
is less than five: if leading
"\&!"
arguments can be stripped such that only one argument remains then a string
length test is performed (again, even if the argument is a unary operator); if
leading
"\&!"
arguments can be stripped such that three arguments remain and the second
argument is a binary operator, then the binary operation is performed (even
if the first argument is a unary operator, including an unstripped
"\&!")).

Note:
A common mistake is to use
if \&[ $foo = bar \&]
which fails if parameter
foo
is
NULL
or unset, if it has embedded spaces (i.e.\&
IFS
characters), or if it is a unary operator like
\&!
or
-n.
Use tests like
if \&[ \&"X$foo\&" = Xbar \&]
instead.

time
[-p]
[pipeline]
If a
pipeline
is given, the times used to execute the pipeline are reported.
If no pipeline
is given, then the user and system time used by the shell itself, and all the
commands it has run since it was started, are reported.
The times reported are the real time (elapsed time from start to finish),
the user CPU time (time spent running in user mode), and the system CPU time
(time spent running in kernel mode).
Times are reported to standard error; the format of the output is:

"0m0.00s real 0m0.00s user 0m0.00s system"

If the
-p
option is given the output is slightly longer:

real 0.00
user 0.00
sys 0.00

It is an error to specify the
-p
option unless
pipeline
is a simple command.

Simple redirections of standard error do not affect the output of the
time
command:

$ time sleep 1 2\*(Gt afile$ { time sleep 1; } 2\*(Gt afile

Times for the first command do not go to
afile,
but those of the second command do.

times

Print the accumulated user and system times used both by the shell
and by processes that the shell started which have exited.
The format of the output is:

0m0.00s 0m0.00s
0m0.00s 0m0.00s

trap[handlersignal]...

Sets a trap handler that is to be executed when any of the specified signals are
received.
handler
is either a
NULL
string, indicating the signals are to be ignored, a minus sign
(-),
indicating that the default action is to be taken for the signals (see
signal(3/)),
or a string containing shell commands to be evaluated and executed at the first
opportunity (i.e. when the current command completes, or before printing the
next
PS1
prompt) after receipt of one of the signals.
signal
is the name of a signal (e.g.\&
PIPE
or
ALRM)
or the number of the signal (see the
kill-l
command above).

There are two special signals:
EXIT
(also known as 0), which is executed when the shell is about to exit, and
ERR,
which is executed after an error occurs (an error is something that would cause
the shell to exit if the
-e
or
errexit
option were set \- see the
set
command above).
EXIT
handlers are executed in the environment of the last executed command.
Note
that for non-interactive shells, the trap handler cannot be changed for signals
that were ignored when the shell started.

With no arguments,
trap
lists, as a series of
trap
commands, the current state of the traps that have been set since the shell
started.
Note that the output of
trap
cannot be usefully piped to another process (an artifact of the fact that
traps are cleared when subprocesses are created).

The original Korn shell's
DEBUG
trap and the handling of
ERR
and
EXIT
traps in functions are not yet implemented.

true

A command that exits with a zero value.

typeset
.Oo Op Ic +-lprtUux
[-L ]
[-R ]
[-Z ]
[-i ]
\*(Ba -f [-tux Oc]
.Oo Ar name
[]
...Oc
Display or set parameter attributes.
With no
name
arguments, parameter attributes are displayed; if no options are used, the
current attributes of all parameters are printed as
typeset
commands; if an option is given (or
"-"
with no option letter), all parameters and their values with the specified
attributes are printed; if options are introduced with
"+",
parameter values are not printed.

If
name
arguments are given, the attributes of the named parameters are set
(-)
or cleared
(+).
Values for parameters may optionally be specified.
If
typeset
is used inside a function, any newly created parameters are local to the
function.

When
-f
is used,
typeset
operates on the attributes of functions.
As with parameters, if no
name
arguments are given,
functions are listed with their values (i.e. definitions) unless
options are introduced with
"+",
in which case only the function names are reported.

-f

Function mode.
Display or set functions and their attributes, instead of parameters.

-i

Integer attribute.
n
specifies the base to use when displaying the integer (if not specified, the
base given in the first assignment is used).
Parameters with this attribute may
be assigned values containing arithmetic expressions.

-L

Left justify attribute.
n
specifies the field width.
If
n
is not specified, the current width of a parameter (or the width of its first
assigned value) is used.
Leading whitespace (and zeros, if used with the
-Z
option) is stripped.
If necessary, values are either truncated or space padded
to fit the field width.

-l

Lower case attribute.
All upper case characters in values are converted to lower case.
(In the original Korn shell, this parameter meant
long integer
when used with the
-i
option.)

-p

Print complete
typeset
commands that can be used to re-create the attributes (but not the values) of
parameters.
This is the default action (option exists for ksh93 compatibility).

-R

Right justify attribute.
n
specifies the field width.
If
n
is not specified, the current width of a parameter (or the width of its first
assigned value) is used.
Trailing whitespace is stripped.
If necessary, values are either stripped of leading characters or space
padded to make them fit the field width.

-r

Read-only attribute.
Parameters with this attribute may not be assigned to or unset.
Once this attribute is set, it cannot be turned off.

-t

Tag attribute.
Has no meaning to the shell; provided for application use.

For functions,
-t
is the trace attribute.
When functions with the trace attribute are executed, the
xtrace
(-x)
shell option is temporarily turned on.

-U

Unsigned integer attribute.
Integers are printed as unsigned values (only
useful when combined with the
-i
option).
This option is not in the original Korn shell.

-u

Upper case attribute.
All lower case characters in values are converted to upper case.
(In the original Korn shell, this parameter meant
unsigned integer
when used with the
-i
option, which meant upper case letters would never be used for bases greater
than 10.
See the
-U
option.)

For functions,
-u
is the undefined attribute.
See
above for the implications of this.

-x

Export attribute.
Parameters (or functions) are placed in the environment of
any executed commands.
Exported functions are not yet implemented.

-Z

Zero fill attribute.
If not combined with
-L,
this is the same as
-R,
except zero padding is used instead of space padding.

ulimit
[-acdfHlmnpSst [value]]
...
Display or set process limits.
If no options are used, the file size limit
(-f)
is assumed.
value,
if specified, may be either an arithmetic expression starting with a
number or the word
unlimited.
The limits affect the shell and any processes created by the shell after a
limit is imposed; limits may not be increased once they are set.

-a

Display all limits; unless
-H
is used, soft limits are displayed.

-c n

Impose a size limit of
n
blocks on the size of core dumps.

-d n

Impose a size limit of
n
kilobytes on the size of the data area.

-f n

Impose a size limit of
n
blocks on files written by the shell and its child processes (files of any
size may be read).

-H

Set the hard limit only (the default is to set both hard and soft limits).

-l n

Impose a limit of
n
kilobytes on the amount of locked (wired) physical memory.

-m n

Impose a limit of
n
kilobytes on the amount of physical memory used.

-n n

Impose a limit of
n
file descriptors that can be open at once.

-p n

Impose a limit of
n
processes that can be run by the user at any one time.

-S

Set the soft limit only (the default is to set both hard and soft limits).

-s n

Impose a size limit of
n
kilobytes on the size of the stack area.

-t n

Impose a time limit of
n
CPU seconds spent in user mode to be used by each process.

As far as
ulimit
is concerned, a block is 512 bytes.

umask
[-S]
[mask]
Display or set the file permission creation mask, or umask (see
umask(2/)).
If the
-S
option is used, the mask displayed or set is symbolic; otherwise, it is an
octal number.

Symbolic masks are like those used by
chmod(1).
When used, they describe what permissions may be made available (as opposed to
octal masks in which a set bit means the corresponding bit is to be cleared).
For example,
ug=rwx,o=
sets the mask so files will not be readable, writable, or executable by
others,
and is equivalent (on most systems) to the octal mask
007.

unalias
[-adt]
[name]...
The aliases for the given names are removed.
If the
-a
option is used, all aliases are removed.
If the
-t
or
-d
options are used, the indicated operations are carried out on tracked or
directory aliases, respectively.

unset
[-fv]
parameter...
Unset the named parameters
(
-v,
the default
)
or functions
(-f).
The exit status is non-zero if any of the parameters were already unset, zero
otherwise.

wait[job]...

Wait for the specified job(s) to finish.
The exit status of
wait
is that of the last specified job; if the last job is killed by a signal, the
exit status is 128 + the number of the signal (see
kill-l exit-status
above); if the last specified job can't be found (because it never existed, or
had already finished), the exit status of
wait
is 127.
See
below for the format of
job.
wait
will return if a signal for which a trap has been set is received, or if a
SIGHUP,
SIGINT,
or
SIGQUIT
signal is received.

If no jobs are specified,
wait
waits for all currently running jobs (if any) to finish and exits with a zero
status.
If job monitoring is enabled, the completion status of jobs is printed
(this is not the case when jobs are explicitly specified).

whence
[-pv]
[name]...
For each
name,
the type of command is listed (reserved word, built-in, alias,
function, tracked alias, or executable).
If the
-p
option is used, a path search is performed even if
name
is a reserved word, alias, etc.
Without the
-v
option,
whence
is similar to
command-v
except that
whence
will find reserved words and won't print aliases as alias commands.
With the
-v
option,
whence
is the same as
command-V.
Note that for
whence,
the
-p
option does not affect the search path used, as it does for
command.
If the type of one or more of the names could not be determined, the exit
status is non-zero.

Job control

Job control refers to the shell's ability to monitor and control jobs, which
are processes or groups of processes created for commands or pipelines.
At a minimum, the shell keeps track of the status of the background (i.e.\&
asynchronous) jobs that currently exist; this information can be displayed
using the
jobs
commands.
If job control is fully enabled (using
set-m
or
set-o monitor),
as it is for interactive shells, the processes of a job are placed in their
own process group.
Foreground jobs can be stopped by typing the suspend
character from the terminal (normally ^Z), jobs can be restarted in either the
foreground or background using the
fg
and
bg
commands, and the state of the terminal is saved or restored when a foreground
job is stopped or restarted, respectively.

When a job is created, it is assigned a job number.
For interactive shells, this number is printed inside
[..][..],
followed by the process IDs of the processes in the job when an asynchronous
command is run.
A job may be referred to in the
bg,
fg,
jobs,
kill,
and
wait
commands either by the process ID of the last process in the command pipeline
(as stored in the
$!\&
parameter) or by prefixing the job number with a percent
sign
(%).
Other percent sequences can also be used to refer to jobs:

%+ \*(Ba %% \*(Ba %

The most recently stopped job, or, if there are no stopped jobs, the oldest
running job.

%-

The job that would be the
%+
job if the latter did not exist.

%

The job with job number
n.

%?

The job with its command containing the string
string
(an error occurs if multiple jobs are matched).

%

The job with its command starting with the string
string
(an error occurs if multiple jobs are matched).

When a job changes state (e.g. a background job finishes or foreground job is
stopped), the shell prints the following status information:

[ Ns Ar number ] Ar flag status command

where...

number

is the job number of the job;

flag

is the
"+"
or
"-"
character if the job is the
%+
or
%-
job, respectively, or space if it is neither;

status

indicates the current state of the job and can be:

Done [number]

The job exited.
number
is the exit status of the job, which is omitted if the status is zero.

Running

The job has neither stopped nor exited (note that running does not necessarily
mean consuming CPU time \-
the process could be blocked waiting for some event).

Stopped [signal]

The job was stopped by the indicated
signal
(if no signal is given, the job was stopped by
SIGTSTP)).

signal-description[core dumped]

The job was killed by a signal (e.g. memory fault, hangup); use
kill-l
for a list of signal descriptions.
The
core dumped
message indicates the process created a core file.

command

is the command that created the process.
If there are multiple processes in
the job, each process will have a line showing its
command
and possibly its
status,
if it is different from the status of the previous process.

When an attempt is made to exit the shell while there are jobs in the stopped
state, the shell warns the user that there are stopped jobs and does not exit.
If another attempt is immediately made to exit the shell, the stopped jobs are
sent a
SIGHUP
signal and the shell exits.
Similarly, if the
nohup
option is not set and there are running jobs when an attempt is made to exit
a login shell, the shell warns the user and does not exit.
If another attempt
is immediately made to exit the shell, the running jobs are sent a
SIGHUP
signal and the shell exits.

Interactive input line editing

The shell supports three modes of reading command lines from a
tty(4)
in an interactive session, controlled by the
emacs,
gmacs,
and
vi
options (at most one of these can be set at once).
The default is
emacs.
Editing modes can be set explicitly using the
set
built-in, or implicitly via the
EDITOR
and
VISUAL
environment variables.
If none of these options are enabled,
the shell simply reads lines using the normal
tty(4)
driver.
If the
emacs
or
gmacs
option is set, the shell allows emacs-like editing of the command; similarly,
if the
vi
option is set, the shell allows vi-like editing of the command.
These modes are described in detail in the following sections.

In these editing modes, if a line is longer than the screen width (see the
COLUMNS
parameter),
a
"\*(Gt",
"+",
or
"\*(Lt"
character is displayed in the last column indicating that there are more
characters after, before and after, or before the current position,
respectively.
The line is scrolled horizontally as necessary.

Emacs editing mode

When the
emacs
option is set, interactive input line editing is enabled.
Warning: This mode is
slightly different from the emacs mode in the original Korn shell.
In this mode, various editing commands
(typically bound to one or more control characters) cause immediate actions
without waiting for a newline.
Several editing commands are bound to particular
control characters when the shell is invoked; these bindings can be changed
using the
bind
command.

The following is a list of available editing commands.
Each description starts with the name of the command,
suffixed with a colon;
an
[n]
(if the command can be prefixed with a count); and any keys the command is
bound to by default, written using caret notation
e.g. the ASCII ESC character is written as ^[.
^[A-Z] sequences are not case sensitive.
A count prefix for a command is entered using the sequence
.Pf ^[ Ns Ar n ,
where
n
is a sequence of 1 or more digits.
Unless otherwise specified, if a count is
omitted, it defaults to 1.

Note that editing command names are used only with the
bind
command.
Furthermore, many editing commands are useful only on terminals with
a visible cursor.
The default bindings were chosen to resemble corresponding
Emacs key bindings.
The user's
tty(4)
characters (e.g.\&
ERASE)
are bound to
reasonable substitutes and override the default bindings.

abort: ^C, ^G

Useful as a response to a request for a
search-history
pattern in order to abort the search.

auto-insert: [n]

Simply causes the character to appear as literal input.
Most ordinary characters are bound to this.

[n]
^B , ^XD
Moves the cursor backward
n
characters.

[n]
^[b
Moves the cursor backward to the beginning of the word; words consist of
alphanumerics, underscore
(_),
and dollar sign
($)
characters.

beginning-of-history: ^[\*(Lt

Moves to the beginning of the history.

beginning-of-line: ^A

Moves the cursor to the beginning of the edited input line.

[n]
^[C , ^[c
Uppercase the first character in the next
n
words, leaving the cursor past the end of the last word.

comment: ^[#

If the current line does not begin with a comment character, one is added at
the beginning of the line and the line is entered (as if return had been
pressed); otherwise, the existing comment characters are removed and the cursor
is placed at the beginning of the line.

complete: ^[^[

Automatically completes as much as is unique of the command name or the file
name containing the cursor.
If the entire remaining command or file name is
unique, a space is printed after its completion, unless it is a directory name
in which case
"/"
is appended.
If there is no command or file name with the current partial word
as its prefix, a bell character is output (usually causing a beep to be
sounded).

complete-command: ^X^[

Automatically completes as much as is unique of the command name having the
partial word up to the cursor as its prefix, as in the
complete
command above.

complete-file: ^[^X

Automatically completes as much as is unique of the file name having the
partial word up to the cursor as its prefix, as in the
complete
command described above.

complete-list: ^I, ^[=

Complete as much as is possible of the current word,
and list the possible completions for it.
If only one completion is possible,
match as in the
complete
command above.

[n]
ERASE , ^? , ^H
Deletes
n
characters before the cursor.

delete-char-forward: [n]

Deletes
n
characters after the cursor.

[n]
ERASE , ^[^? , ^[^H , ^[h
Deletes
n
words before the cursor.

[n]
^[d
Deletes characters after the cursor up to the end of
n
words.

[n]
^N , ^XB
Scrolls the history buffer forward
n
lines (later).
Each input line originally starts just after the last entry
in the history buffer, so
down-history
is not useful until either
search-history
or
up-history
has been performed.

[n]
^[L , ^[l
Lowercases the next
n
words.

end-of-history: ^[\*(Gt

Moves to the end of the history.

end-of-line: ^E

Moves the cursor to the end of the input line.

eot: ^_

Acts as an end-of-file; this is useful because edit-mode input disables
normal terminal input canonicalization.

[n]
^D
Acts as
eot
if alone on a line; otherwise acts as
delete-char-forward.

error:

Error (ring the bell).

exchange-point-and-mark: ^X^X

Places the cursor where the mark is and sets the mark to where the cursor was.

expand-file: ^[*

Appends a
"*"
to the current word and replaces the word with the result of performing file
globbing on the word.
If no files match the pattern, the bell is rung.

[n]
^F , ^XC
Moves the cursor forward
n
characters.

[n]
^[f
Moves the cursor forward to the end of the
n
word.

[n]
^[g
Goes to history number
n.

kill-line: KILL

Deletes the entire input line.

kill-region: ^W

Deletes the input between the cursor and the mark.

[n]
^K
Deletes the input from the cursor to the end of the line if
n
is not specified; otherwise deletes characters between the cursor and column
n.

list: ^[?

Prints a sorted, columnated list of command names or file names (if any) that
can complete the partial word containing the cursor.
Directory names have
"/"
appended to them.

list-command: ^X?

Prints a sorted, columnated list of command names (if any) that can complete
the partial word containing the cursor.

list-file: ^X^Y

Prints a sorted, columnated list of file names (if any) that can complete the
partial word containing the cursor.
File type indicators are appended as described under
list
above.

newline: ^J , ^M

Causes the current input line to be processed by the shell.
The current cursor position may be anywhere on the line.

newline-and-next: ^O

Causes the current input line to be processed by the shell, and the next line
from history becomes the current line.
This is only useful after an
up-history
or
search-history.

no-op: QUIT

This does nothing.

prefix-1: ^[

Introduces a 2-character command sequence.

prefix-2: ^X , ^[[ , ^[O

Introduces a 2-character command sequence.

[n]
^[. , ^[_
The last
(n)
word of the previous command is inserted at the cursor.

quote: ^^

The following character is taken literally rather than as an editing command.

redraw: ^L

Reprints the prompt string and the current input line.

[n]
^[^]
Search backward in the current line for the
n
occurrence of the next character typed.

[n]
^]
Search forward in the current line for the
n
occurrence of the next character typed.

search-history: ^R

Enter incremental search mode.
The internal history list is searched
backwards for commands matching the input.
An initial
"^"
in the search string anchors the search.
The abort key will leave search mode.
Other commands will be executed after leaving search mode.
Successive
search-history
commands continue searching backward to the next previous occurrence of the
pattern.
The history buffer retains only a finite number of lines; the oldest
are discarded as necessary.

set-mark-command: ^[

Set the mark at the cursor position.

stuff:

On systems supporting it, pushes the bound character back onto the terminal
input where it may receive special processing by the terminal handler.
This is useful for the BRL ^T mini-systat feature, for example.

stuff-reset:

Acts like
stuff,
then aborts input the same as an interrupt.

transpose-chars: ^T

If at the end of line, or if the
gmacs
option is set, this exchanges the two previous characters; otherwise, it
exchanges the previous and current characters and moves the cursor one
character to the right.

[n]
^P , ^XA
Scrolls the history buffer backward
n
lines (earlier).

[n]
^[U , ^[u
Uppercase the next
n
words.

quote: ^V

Synonym for ^^.

yank: ^Y

Inserts the most recently killed text string at the current cursor position.

yank-pop: ^[y

Immediately after a
yank,
replaces the inserted text string with the next previously killed text string.

Vi editing mode

The vi command-line editor in
ksh
has basically the same commands as the
vi(1)
editor with the following exceptions:

The
_
command is different (in
ksh
it is the last argument command; in
vi(1)
it goes to the start of the current line).

The
/
and
G
commands move in the opposite direction to the
j
command.

Commands which don't make sense in a single line editor are not available
(e.g. screen movement commands and
ex(1/Ns)
colon
(\&:)
commands).

Note that the ^X stands for control-X; also
esc,
space,
and
tab
are used for escape, space, and tab, respectively (no kidding).

Like
vi(1),
there are two modes:
insert
mode and
command
mode.
In insert mode, most characters are simply put in the buffer at the
current cursor position as they are typed; however, some characters are
treated specially.
In particular, the following characters are taken from current
tty(4)
settings
(see
stty(1))
and have their usual meaning (normal values are in parentheses): kill (^U),
erase (^?), werase (^W), eof (^D), intr (^C), and quit (^\e).
In addition to
the above, the following characters are also treated specially in insert mode:

^E

Command and file name enumeration (see below).

^F

Command and file name completion (see below).
If used twice in a row, the
list of possible completions is displayed; if used a third time, the completion
is undone.

^H

Erases previous character.

^J \*(Ba ^M

End of line.
The current line is read, parsed, and executed by the shell.

^V

Literal next.
The next character typed is not treated specially (can be used
to insert the characters being described here).

In command mode, each character is interpreted as a command.
Characters that
don't correspond to commands, are illegal combinations of commands, or are
commands that can't be carried out, all cause beeps.
In the following command descriptions, an
[n]
indicates the command may be prefixed by a number (e.g.\&
10l
moves right 10 characters); if no number prefix is used,
n
is assumed to be 1 unless otherwise specified.
The term
current position
refers to the position between the cursor and the character preceding the
cursor.
A
word
is a sequence of letters, digits, and underscore characters or a sequence of
non-letter, non-digit, non-underscore, and non-whitespace characters (e.g.\&
ab2*&^
contains two words) and a
big-word
is a sequence of non-whitespace characters.

Special
ksh
vi commands:

The following commands are not in, or are different from, the normal vi file
editor:

.Oo Ar n Oc Ns _
Insert a space followed by the
n
big-word from the last command in the history at the current position and enter
insert mode; if
n
is not specified, the last word is inserted.

#

Insert the comment character
(#)
at the start of the current line and return the line to the shell (equivalent
to
I#^J)).

.Oo Ar n Oc Ns g
Like
G,
except if
n
is not specified, it goes to the most recent remembered line.

.Oo Ar n Oc Ns v
Edit line
n
using the
vi(1)
editor; if
n
is not specified, the current line is edited.
The actual command executed is
fc-e ${VISUAL:-${EDITOR:-vi}} n.

* and ^X

Command or file name expansion is applied to the current big-word (with an
appended
"*"
if the word contains no file globbing characters) \- the big-word is replaced
with the resulting words.
If the current big-word is the first on the line
or follows one of the characters
"\&;",
"|",
"&",
"(",
or
"\&)",
and does not contain a slash
(/),
then command expansion is done; otherwise file name expansion is done.
Command expansion will match the big-word against all aliases, functions, and
built-in commands as well as any executable files found by searching the
directories in the
PATH
parameter.
File name expansion matches the big-word against the files in the
current directory.
After expansion, the cursor is placed just past the last
word and the editor is in insert mode.

.Oo Ar n Oc Ns \e ,
.Oo Ar n Oc Ns ^F ,
.Oo Ar n Oc Ns Aq tab ,
and
.Oo Ar n Oc Ns Aq esc
Command/file name completion.
Replace the current big-word with the
longest unique match obtained after performing command and file name expansion.
tab
is only recognized if the
vi-tabcomplete
option is set, while
esc
is only recognized if the
vi-esccomplete
option is set (see
set-o).
If
n
is specified, the
n
possible completion is selected (as reported by the command/file name
enumeration command).

= and ^E

Command/file name enumeration.
List all the commands or files that match the current big-word.

@

Macro expansion.
Execute the commands found in the alias
c.

Intra-line movement commands:

.Oo Ar n Oc Ns h and
.Oo Ar n Oc Ns ^H
Move left
n
characters.

.Oo Ar n Oc Ns l and
.Oo Ar n Oc Ns Aq space
Move right
n
characters.

0

Move to column 0.

^

Move to the first non-whitespace character.

.Oo Ar n Oc Ns \*(Ba
Move to column
n.

$

Move to the last character.

.Oo Ar n Oc Ns b
Move back
n
words.

.Oo Ar n Oc Ns B
Move back
n
big-words.

.Oo Ar n Oc Ns e
Move forward to the end of the word,
n
times.

.Oo Ar n Oc Ns E
Move forward to the end of the big-word,
n
times.

.Oo Ar n Oc Ns w
Move forward
n
words.

.Oo Ar n Oc Ns W
Move forward
n
big-words.

%

Find match.
The editor looks forward for the nearest parenthesis, bracket, or
brace and then moves the cursor to the matching parenthesis, bracket, or brace.

.Oo Ar n Oc Ns G
Move to line
n
in the history; if
n
is not specified, the number of the first remembered line is used.

.Oo Ar n Oc Ns g
Like
G,
except if
n
is not specified, it goes to the most recent remembered line.

.Oo Ar n Oc Ns / Ns Ar string
Search backward through the history for the
n
line containing
string;
if
string
starts with
"^",
the remainder of the string must appear at the start of the history line for
it to match.

.Oo Ar n Oc Ns \&? Ns Ar string
Same as
/,
except it searches forward through the history.

.Oo Ar n Oc Ns n
Search for the
n
occurrence of the last search string;
the direction of the search is the same as the last search.

.Oo Ar n Oc Ns N
Search for the
n
occurrence of the last search string;
the direction of the search is the opposite of the last search.

Edit commands

.Oo Ar n Oc Ns a
Append text
n
times; goes into insert mode just after the current position.
The append is
only replicated if command mode is re-entered i.e.\&
esc
is used.

.Oo Ar n Oc Ns A
Same as
a,
except it appends at the end of the line.

.Oo Ar n Oc Ns i
Insert text
n
times; goes into insert mode at the current position.
The insertion is only
replicated if command mode is re-entered i.e.\&
esc
is used.

.Oo Ar n Oc Ns I
Same as
i,
except the insertion is done just before the first non-blank character.

Substitute whole line.
All characters from the first non-blank character to the
end of the line are deleted and insert mode is entered.

.Oo Ar n Oc Ns c Ns Ar move-cmd
Change from the current position to the position resulting from
nmove-cmd
(i.e. delete the indicated region and go into insert mode); if
move-cmd
is
c,
the line starting from the first non-blank character is changed.

C

Change from the current position to the end of the line (i.e. delete to the
end of the line and go into insert mode).

.Oo Ar n Oc Ns x
Delete the next
n
characters.

.Oo Ar n Oc Ns X
Delete the previous
n
characters.

D

Delete to the end of the line.

.Oo Ar n Oc Ns d Ns Ar move-cmd
Delete from the current position to the position resulting from
nmove-cmd ;
move-cmd
is a movement command (see above) or
d,
in which case the current line is deleted.

VERSION

This page documents version @(#)PD KSH v5.2.14 99/07/13.2 of the public
domain Korn shell.

AUTHORS

This shell is based on the public domain 7th edition Bourne shell clone by
Charles Forsyth and parts of the BRL shell by Doug A. Gwyn, Doug Kingston,
Ron Natalie, Arnold Robbins, Lou Salkind, and others.
The first release of
pdksh
was created by Eric Gisin, and it was subsequently maintained by John R.\&
MacMillan (change!john@sq.sq.com), Simon J. Gerraty (sjg@zen.void.oz.au),
and Michael Rendell (michael@cs.mun.ca).
The
CONTRIBUTORS
file in the source distribution contains a more complete list of people and
their part in the shell's development.